The present invention relates in general to magnetic brush development apparatus for applying developer material to a latent image in an electrostatographic reproduction apparatus, and more particularly to an improved magnetic brush development apparatus including a device for assuring substantially balanced developer material flow distribution in such apparatus.
Magnetic brush development apparatus for applying developer material to a latent image in an electrostatographic reproduction apparatus are well known in the art. Such apparatus may include a housing having a sump portion which contains a supply of developer material. When the developer material comprises a mixture of carrier particles and smaller pigmented marking particles, the material in the sump is agitated to triboelectrically charge the material prior to delivering it to a magnetic brush where it can be brought into association with, and electrostatically transferred to, an electrostatic latent image to develop such image.
Copending, commonly assigned U.S. Pat. application Ser. No. 597,323, now U.S. Pat. No. 4,887,132, filed April 6, 1984 in the names of Joseph et al, and U.S. Pat. No. 4,671,207, issued June 9, 1987, in the name of Hilbert disclose magnetic brush development apparatus particularly suitable for use with development material having pigmented marking particles and permanent magnetic carrier particles, such as disclosed in U.S. Pat. No. 4,546,060, issued Oct. 8, 1985, in the names of Miskinis et al. More particularly, the disclosed apparatus include a ribbon blender that is used for agitating (mixing), feeding and triboelectrically charging such material in the sump portion of a magnetic brush development apparatus, and a feed mechanism that delivers material from the sump portion to a magnetic brush. The ribbon blender is constructed to provide uniform flow distribution of developer material across the length of the apparatus so that a sufficient supply of material is delivered to the magnetic brush over its full extent to develop the entire latent electrostatic image. It has been found that under certain conditions developer material tends to pump toward one end of the apparatus. Accordingly, insufficient material is delivered to areas of the magnetic brush to satisfactorily develop the entire latent electrostatic image creating copy defects such as voids or under developed regions. Such conditions causing developer material pumping result from a variety of diverse parameters which include for example sump wall smoothness and developer material charge-to-mass ratio.